Powertrain Control Hardware
POWERTRAIN CONTROL HARDWARE
Powertrain Control Module (PCM)
The center of the electronic engine control (EEC) system is the PCM. The PCM contains both engine and transmission microprocessors. Operating information, as well as concern information, is communicated between the 2 processors through controller area network (CAN) communications. Both can be programmed individually, however, a new PCM is installed as an assembly. The PCM has 3 electrical connectors (122 pins total). The PCM receives input from sensors and other electronic components (switches and relays) and places this information into random access memory (RAM) or keep alive memory (KAM). Based on information programmed into its read-only memory (ROM), the PCM generates output signals to control various relays, solenoids, and actuators. For vehicles equipped with manual transmissions, only 2 electrical connectors are used.
The transmission control module (TCM) controls the power monitor strategy. The power monitor monitors the engine speed at idle. If an abnormal engine speed increase is detected, the power monitor commands the fuel injector control module (FICM) off in an effort to maintain a normal idle speed. For manual transmission vehicles, the power monitor is the only active TCM function. Diagnostic trouble codes (DTCs) are stored if the power monitor is active.
Fuel Injector Control Module (FICM)
The FICM requires a 12-volt power source. The FICM receives power from the vehicle batteries through the FICM relay contacts each time the key is turned to the ON position. As the key is turned to the ON position, the FICM provides an internal ground to the coil side of the FICM relay. This closes the relay contacts and provides the FICM with the necessary power. The PCM communicates with the FICM using the CAN protocol. The CAN protocol is an international standards organization (ISO) standard for serial data communication. The CAN protocol standard includes a physical layer using differential transmission on a twisted pair of wires and a data link layer that defines different message types, arbitration rules for bus access, methods for concern detection and concern confinement. The FICM receives information from the PCM, including the volume of fuel desired, RPM, engine oil temperature, injection control pressure, and others. The FICM uses those signals to calculate fuel injection and duration. After calculating injector fuel delivery time, the FICM sends 48 volts at a 20-amp pulse to the correct injector so that the correct amount of fuel is delivered to the cylinder at the correct time.
The FICM has four high side driver outputs; two for the right bank and two for the left bank. The high side driver output function distributes energy to the correct bank based on a camshaft position output (CMPO) signal, and provides regulated current to the injectors. The PCM commands the fuel quantity and the FICM controls the duration and timing of the injection event. The FICM's low side driver outputs control the sequencing (firing order) of the engine.
Glow Plug Control Module (GPCM)
Glow Plug Control Module (GPCM):
NOTE: The wait-to-start indicator on-time is controlled by the PCM and is independent from the GPCM on-time.
The glow plug system consists of a solid state GPCM, glow plugs, and the associated wiring harness. The glow plug on-time is controlled by the PCM and is a function of oil temperature, barometric pressure, and battery voltage. The PCM enables the GPCM to power the individual glow plugs by providing direct battery voltage to the glow plugs. The GPCM monitors the individual glow plug operation. Concerns detected by the GPCM are transmitted to the PCM using a serial communication signal on a diagnostic line. Glow plug on-time normally varies between 1 to 120 seconds. In addition to PCM control, the GPCM internally limits the glow plug operation to 180 seconds regardless of the PCM commanded on-time. The power to the glow plugs is provided through the GPCM solid state drivers directly from the vehicle battery. The GPCM monitors and detects individual glow plug functionality and the control and communication links to the PCM.
Keep Alive Memory (KAM)
The PCM stores information in KAM (a memory integrated circuit chip) about vehicle operating conditions, and then uses this information to compensate for component variability. KAM remains powered when the vehicle key is off so that this information is not lost.
Power and Ground Signals
Gold Plated Pins
NOTE: When installing new terminals make sure new gold plated terminals are used where gold plated terminals where originally used.
Some engine control hardware has gold plated pins within the connectors and mating harness connectors to improve electrical stability for low current draw circuits and to enhance corrosion resistance. The EEC components equipped with gold terminals vary by vehicle application.
Keep Alive Power (KAPWR)
The PCM stores the vehicle operating conditions in the KAM and uses this information to compensate for component variability. The KAPWR circuit supplies a constant battery voltage (B+) input to the PCM to maintain the memory contents when the key is in the OFF position.
Power Ground (PWR GND)
The PWR GND circuit(s) is directly connected to the battery negative terminal. PWR GND provides a return path for the PCM VPWR circuits.
Reference Voltage (VREF)
VREF is a consistent positive voltage (5.0 volts ± 0.5) provided by the PCM. VREF is typically used by 3-wire sensors and some digital input signals.
Signal Return (SIG RTN)
The SIG RTN circuit(s) is a dedicated return path for VREF applied components.
Vehicle Buffered Power (VBPWR)
VBPWR is a regulated voltage supplied by the PCM to vehicle sensors. These sensors require a constant 12 volts for operation and cannot withstand VPWR voltage variations. VBPWR is regulated to VPWR minus 1.5 volts and is also current limited to protect the sensors.
Vehicle Power (VPWR)
VPWR is the primary source of PCM power. VPWR is switched through the PCM power relay and is controlled by the ignition switch. With the key in the START or RUN position, voltage is supplied to the PCM power relay coil. The supplied voltage energizes the relay and closes the internal relay contacts. With the relay contacts closed, VPWR is supplied to the PCM.